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Arthrosis

by M. Be'ly, M.D

The Roger Wyburn-Mason and Jack M. Blount Foundation for the

Eradication of Rheumatoid Disease

aka The Arthritis Trust of America

7376 Walker Road, Fairview, Tn 37062

Originally published in

Editor’s note: Dr. Be'ly presents an excellent description of the

pathologic processes in degenerative arthritis and a report on ex-

perimental osteoarthritis produced in rats by sodium fluoride. The

relation of fluoridated water to the human disease is under further

investigation in Hungary.

Miklos Be'ly, M.D.

Osteoarthritis is a degenerative process leading to progressive

damage of the articular cartilage and secondary disintegration of the

articular surface of bones. Several factors are known to have a role

in the pathogenesis of the disease in secondary arthrosis. If the

etiologic factor is unknown, the term idiopathic or primary arthrosis

is used.

The degenerative process takes place in the articular cartilage,

consisting of chondrocytes and intercellular matrix. The intercellular

matrix is formed by a structure of collagen fibrils embedded in a

proteoglycan matrix. The collagen fibrils have a characteristic orien-

tation. Originating in the border-line between bone and cartilage, the

fibrils run vertically upward to the surface of the articular cartilage,

there bend and run further parallel with the surface, forming a dense

layer, the so-called lamina splendens. The fibrils of the tangential

zone, that run tangentially to the chondrocytes, are named

“interterritoreal fibrils.” The other part of the collagen fibrils — the

territoreal fibrils — are organized circularly around the chondrocytes.

The territoreal fibrils form sequences of linearly arranged

microspheres.

This particular collagen structure provides the special biome-

chanical characteristics of the articular cartilage. The vertical fibers

ensure resistance against twisting, tracting shearing stress, the lamina

splendens serves as a shield, the linearly arranged microspheres

resist against pressing forces. The lower zone of the articular carti-

lage is sclerosed, so the physio-chemical properties of this zone are

similar to the characteristics of the subchondral bone tissue, provid-

ing firm connection between bone and cartilage.

Four zones can be distinguished from each other in the articular

cartilage according to the orientation of collagen fibrils:

IV: Lower, sclerotic zone.

III: Vertical zone.

II: Zone of bending.

I: Zone parallel with the surface.

The other constituent of the intercellular material is the so-called

matrix. The matrix consists of aggregates, composed by

proteoglycans bound to molecules of hyaluronic acid. The

proteoglycans are mucopolysaccharides (new name:

glycosaminoglycane) bound to carrier proteins. Binding proteins

bind the proteoglycans to molecules of hyaluronic acid. the muco-

polysaccharides — strongly hydrophilic due to their negative charge

— have a main role in the biomechanical properties of the cartilage.

Their great water binding capacity (they can bind as much as 10,000

times larger amounts of water than their own) provides the elasticity

and load bearing potential of the cartilage.

The chondrocytes are responsible for the balance of matrix,

synthesized by them.

According to a generally accepted principle, the metabolic dis-

turbance of chondrocyte activity is in the center of the pathogenesis

of arthrosis in the case of primary arthrosis. The synthesizing activ-

ity of chondrocytes decreases, and probably abnormal matrix struc-

tures are also generated. A part of chondrocytes becomes degener-

ated, so enzymes, further damaging the structure of matrix get re-

leased:

— mucopolysaccharidase, splitting the mucopolysaccharides

off from their carrier proteins;

— protease, breaking up the carrier and binding proteins;

— hyaluronidase, decomposing the molecules of hyaluronic

acid, that keep the proteoglycane aggregates together;

— collagenase, damaging the bridges of collagen fibrils, that

collapse after all.

The fragments of articular cartilage cause synovitis; the en-

zymes, released during the inflammatory process further increase the

enzymatic destruction of chondroid tissue. Because of the damage

of chondroid tissue, the surface of the articular cartilage becomes

incongruent, so the remaining congruent surface gets relatively over-

loaded (unchanged load presses a smaller intact surface). The rela-

tive overload further increases the destruction of the articular carti-

lage. The degenerative process is a so-called vicious circle. The

cause that starts the vicious circle is known in secondary arthrosis.

For example, in the case of syringomyelia, or tabes dorsalis, the

vicious circle is started by the overload of articular surface due to the

disturbance of bathyesthesia of joints. In the case of haemarthrosis,

positive ions accumulate in the joint, so the negative charge of muco-

polysaccharides becomes neutralized. The mucopolysaccharides,

therefore, lose their water-binding capacity, so the elasticity and load-

bearing potential of the articular cartilage decreases.

In the case of ochronosis, a pathologic metabolite, the

homogentisine acid destroys the chondrocytes, the synthesizing po-

tential of chondrocytes decreases, and enzymes further damaging the

matrix get released.

Four clinical-radiological stages of arthrosis are distinguished:

Stage I: Mild clinical symptoms appear. Discrete sclerotization

of the cotyloid cavity can be seen on the X-ray picture of the affected

joint, the articular space and the condyle remain intact.

Stage II: The movability of the joint decreases because of the

pain at the start of a movement, and the rigidity of the joint. There

appear small cysts in the cotyloid cavity, and fine osteophytes on the

X-ray picture.